Detecting the number of transmit antennas in a base station

ABSTRACT

Data is scrambled at a transmitter according to one of a number of predetermined scrambling sequences which are associated with a particular one of a number of predetermined transmit antenna diversity schemes (i.e., a specific number of transmit antenna ports). Received data is decoded using one or more of the known transmit antenna diversity schemes and the scrambled data is descrambled according to a corresponding descrambling sequence (related to the scrambling sequence). Based on the descrambled data, the receiver determines which transmit antenna diversity scheme (i.e., the number of antenna ports) is used by the transmitter. In one specific embodiment, CRC parity data is scrambled in the transmitter and the receiver descrambles the recovered CRC parity data according to a descrambling sequence, computes CRC parity data from the received data, and compares the descrambled CRC parity data to the newly computed CRC parity data.

CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY

The present application is a continuation of U.S. patent applicationSer. No. 12/221,867, entitled “DETECTING THE NUMBER OF TRANSMIT ANTENNASIN A BASE STATION”, filed on Aug. 7, 2008, now U.S. Pat. No. 8,290,088which claims priority to U.S. Provisional Patent No. 60/954,357, filedAug. 7, 2007, the entirety of all of which are incorporated herein byreference. Application Ser. No. 12/221,867 is assigned to the assigneeof the present application and is hereby incorporated by reference intothe present application as if fully set forth herein. The presentapplication hereby claims priority under 35 U.S.C. §120 to U.S. patentapplication Ser. No. 12/221,867.

TECHNICAL FIELD OF THE INVENTION

The present application relates generally to wireless communicationsystems, and, more specifically, to user equipment and base stations,and methods for detecting the number of transmit antennas utilized in abase station (e.g., access point) during a communication session.

BACKGROUND OF THE INVENTION

The third generation partnership project (3GPP) is developing a LongTerm Evolution (LTE) specification for the purpose of facilitatingdeployment of broadband services and applications wirelessly.

LTE is designed for uplink speeds up to 50 Mbps and downlink speeds ofup to 100 Mbps for high speed data and media transport. Bandwidth willbe scaleable from 1.25 MHz to 20 MHz. This will provide differentnetwork operators the ability to have different bandwidth allocationsand provide different services based on spectrum. The provision of suchan arrangement of scaleable bandwidth is expected to allow carriers toprovide increased data and voice services over a given bandwidth, sincebandwidth can be more properly matched to the needs of a givenapplication than has heretofore been possible.

LTE employs advanced technologies that are relatively new to wirelesscellular networks, including orthogonal frequency division multiplexing(OFDM) and multiple input multiple output (MIMO) antenna technologies.The uplink utilizes single carrier frequency division multiple access(SC-FDMA) while the downlink employs orthogonal frequency divisionmultiple access (OFDMA). The basic operation and technical descriptionof LTE may be found in the current draft of the 3GPP LTE specification,3GPP (or 3G) Release 8, including 3GPP TX 36.XXX V8.3.0 (2008-05), whichare incorporated herein by reference. The operation and technicaldescription of UMTS may be found in the current draft of the UMTSspecification, SGPP TS 25.XXX, which is incorporated herein byreference.

LTE transmissions are segmented into frames of 10 mSec duration. Eachframe is divided into 10 sub-frames each having two slots. Within eachslot, a number of OFDM symbols (6 or 7) are transmitted. The transmitteddownlink signal includes N subcarriers (15 KHz) for a duration of M OFDMsymbols (typically 6 or 7) which may be represented by a resource grid.FIG. 1 shows an exemplary resource grid illustrating a sub-frame withtwo slots (time; x dimension) and twelve subcarriers (frequency; ydimension). Each slot includes seven OFDM symbols (0 thru 6). As will beappreciated, the total number of subcarriers will depend on the overalltransmission bandwidth.

Each block within the grid is referred to as a resource element (RE).Reference signals/symbols (R) (not shown in FIG. 1) are transmittedduring certain OFDM symbols of each slot and transmitted every sixthsubcarrier (resulting in staggered Rs in both time and frequency).

In OFDMA, users are allocated a specific number of subcarriers(frequency) for a predetermined amount of time. These are referred to asphysical resource blocks (PRBs) which are allocated using a schedulingfunction. A PRB is defined as 12 consecutive subcarriers for one slot.

Within an LTE communication system, base stations may utilize one of anumber of available antenna diversity schemes based on the number oftransmit antenna ports for downlink transmission to the user equipment(UE). In the currently drafted standard, three antenna diversity schemesare provided which correspond to 1, 2 or 4 transmit antenna ports. Thesemay also be referred to as “sets” of transmit antenna ports. While thisconfiguration is exemplary, the base station may have any number (2 orgreater) of transmit antenna ports and thus, may operate in one of anumber of diversity schemes. The UEs include one or more antennas andtransceivers enabling receipt signals transmitted according to theantenna diversity scheme (e.g., 1, 2 or 4 transmit antenna ports).Knowing the number of base station transmit antennas (antennaconfiguration) is critical information for the UE because it isnecessary to decode data transmission correctly after initial access.For example, utilization of two or four base station transmit antennaports, as compared to one, increases system data rates, reliabilityand/or quality of service.

Within the present LTE standard, the synchronization channel(s) do notcarry any transmit antenna configuration information. Under the currentscheme, the UE detects the number of transmit antenna ports bydetermining which transmit antenna diversity scheme is being deployed.Each of the three base station transmission modes (e.g., using 1, 2 or 4transmit antenna ports) has its own antenna diversity scheme: 1 (SingleInput Multiple Output, or SIMO), 2 (Spatial Frequency Block Code, orSFBC) and 4 (Spatial Frequency Block Code-Frequency Switched TransmitDiversity, or SFBC-FSTD). By detecting the appearance of referencesignal (R) subcarriers corresponding to the respective transmit antennaports, the transmit antenna configuration can be determined by the UE.However, the reliability of such blind detection method is poor.

For the two and four transmit antenna modes, the SFBC-based transmitdiversity schemes may be applied to a broadcast channel (BCH) which istransmitted within a predetermined portion of each 10 mSec frame (e.g.,as a portion of the frame). As currently proposed in the LTEspecification, the BCH is transmitted in the first sub-frame (sub-frame0) of each frame and included within OFDM symbols 0 thru 3 in slot 2.The primary and secondary synchronization signals are transmitted in thefirst and sixth sub-frames (sub-frame 0 and sub-frame 5) and includedwithin OFDM symbols 5 and 6 within slot 1 of these sub-frames. This isillustrated in FIG. 2 which shows an example resource grid for sub-frame0 containing the BCH and synchronization channels when transmittingusing 2 transmit antenna ports.

The reference signals are denoted “R1” for transmit antenna port #1 and“R2” for transmit antenna port #2. As is understood, the resourceelements identified as R2 are unused in antenna port #1 transmissionsand those identified as R1 are unused in antenna port #2 transmissions.It will be appreciated that in this diversity scheme (using 2 transmitantenna ports), the resource elements for transmit antenna ports #3 and#4 within the BCH are unused and denoted with an “X”.

The data transmitted in the BCH contains vital system and accessconfiguration information the UE requires in order to access the system,such as system bandwidth, system frame number, basic configurationrequired for further decoding of other information/data, andconfiguration information for various operational features. This channeltypically utilizes a low coding rate as well as 16-bit cyclic redundancycheck (CRC). This system and access configuration information may bereferred to as the BCH transport block data. Thus, the data transmittedin the BCH includes two distinct segments: the transport block data andCRC parity bits (computed from the transport block data). It wasexpected that reception of the BCH would allow the UEs to determine thenumber of transmit antenna ports in the base station by recognizing theantenna diversity scheme.

However, under the proposed scheme, the number of transmit antenna portscannot be adequately detected solely on the basis of the differenttransmit diversity schemes. This is because each transmission scheme hasa large portion of its signal which is identical for all the transmitantenna diversity schemes. Below is a representation of the threeproposed schemes (SIMO (1 antenna port), SFBC (2 antenna ports) andSFBC-FSTD (4 antenna ports)):

$1\mspace{14mu}{antenna}\mspace{14mu}({SIMO})\text{:}\mspace{14mu}\left\lfloor \begin{matrix}S_{1} & S_{2} & S_{3} & S_{4}\end{matrix} \right\rfloor$$2\mspace{14mu}{antennas}\mspace{14mu}({SFBC}){\text{:}\mspace{14mu}\begin{bmatrix}S_{1} & S_{2} & S_{3} & S_{4} \\{- S_{2}^{*}} & S_{1}^{*} & {- S_{4}^{*}} & S_{3}^{*}\end{bmatrix}}$$4\mspace{14mu}{antennas}\mspace{14mu}\left( {{SFBC}\text{-}{FSTD}} \right){\text{:}\mspace{14mu}\begin{bmatrix}S_{1} & S_{2} & 0 & 0 \\0 & 0 & S_{3} & S_{4} \\{- S_{2}^{*}} & S_{1}^{*} & 0 & 0 \\0 & 0 & {- S_{4}^{*}} & S_{3}^{*}\end{bmatrix}}$The columns represent different neighboring subcarriers while the rowsrepresent transmission from different transmit antenna ports. BetweenSIMO and the SFBC transmission fully half of the transmission (e.g.,transmit antenna port #1) is identical. This is also true to a lesserextent between SIMO and SFBC-FSTD where the first two signals (S₁ and S₂for transmit antenna port #1) are identical. Because the coding rates ofthe BCH is extremely low (approximately 1/14), UEs with even moderatelygood channels will be able to correctly decode the BCH using theincorrect number of transmit antenna ports (or diversity scheme). Inoperation, the UEs decode the BCH using each of the three possibleschemes, perform CRC operation on the decoded data, and compare it tothe received CRC. It is possible that a UE may correctly decode the BCHusing the incorrect number of transmit antenna ports. Therefore, the UEmay determine that the base station is transmitting using one scheme (1,2 or 4 transmit antenna ports), when in fact, it is transmitting using adifferent scheme. Additionally, any method which is based on therelative structure of these signals would fail when either one of theantennas channels is in deep fade, or two of the antennas channels arevery similar to each other.

Accordingly, there is needed a more robust and reliable method ofdetecting the number of base station transmit antennas to improveantenna configuration detection performance.

SUMMARY OF THE INVENTION

In accordance with one embodiment, there is provided a method ofgenerating and transmitting transmit antenna port information from atransmitter enabling a remote communications device to determine anumber of transmit antenna ports active in the transmitter. The methodincludes generating data for transmission to a remote communicationdevice and scrambling data bits of the generated data according to oneof a number of predetermined scrambling sequences. Each of thescrambling sequences corresponds to a defined number of transmit antennaports operating within the transmitter. The method further includestransmitting the scrambled data bits within a data frame to the remotecommunication device.

In another embodiment, there is provided a communications device (e.g.,base station) for communicating with a remote communication device in awireless network. The communications device includes a processor andmemory coupled to the processor and operable for storing a number ofscrambling sequences. A transmitter is capable of wirelesslytransmitting data to the remote communications device using one set of apredetermined number of sets of transmit antenna ports, where each setof transmit antenna ports corresponding to a different antenna diversityscheme. The transmitter includes a scrambler for scrambling data bits tobe transmitted in accordance with a one of the stored scramblingsequences, where each of the scrambling sequences is associated with adifferent one of the sets of transmit antenna ports.

In accordance with another embodiment, there is provided a method forreceiving a signal at a receiver from a remote transmitter device anddetermining a number of transmit antenna ports in the remote transmitterdevice. The method includes receiving a signal from a remote transmitterdevice and antenna diversity decoding the received signal into a firstdiversity decoded signal using one of a number of predetermined antennadiversity schemes, where each diversity scheme corresponding to adifferent number of transmit antenna ports. Received scrambled data bitswithin the first diversity decoded signal are descrambled using one of anumber of predetermined de-scrambling sequences corresponding to theplurality of possible diversity schemes. The descrambled data bits areused to determine the number of transmit antenna ports used to transmitthe received signal from the remote transmitter device.

In yet another embodiment, there is a communications device forreceiving a signal from a remote transmitter in a wireless network. Thecommunications device includes a processor; memory coupled to theprocessor and operable for storing a plurality of descramblingsequences; and a receiver capable of wirelessly receiving the signaltransmitted from the remote transmitter using one set of a predeterminednumber of sets of transmit antenna ports, where each set of transmitantenna ports corresponding to a different antenna diversity scheme. Thereceiver includes a descrambler for descrambling received scrambled databits using one of the plurality of stored descrambling sequences, whereeach of the plurality of descrambling sequences corresponds to adifferent one of the sets of transmit antenna ports. The receiver isalso capable of detecting from the descrambled data bits the number oftransmit antenna ports used to transmit the received signal from theremote transmitter.

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, wherein likenumbers designate like objects, and in which:

FIG. 1 depicts a generic resource grid that represents a portion of adownlink signal;

FIG. 2 depicts a similar resource grid illustrating locations ofreference signals, a broadcast channel and synchronization channels;

FIG. 3 depicts a high level diagram of an example communications celland devices within a wireless communications network;

FIG. 4A is a block diagram of a base station shown in FIG. 3;

FIG. 4B is a block diagram of certain components within a transmittershown in FIG. 4A;

FIG. 5A is a block diagram of a user equipment device shown in FIG. 3;

FIG. 5B is a block diagram of certain components within a receiver shownin FIG. 5A; and

FIG. 6 depicts an example resource element grid illustrating broadcastchannel data repeated within the broadcast channel where the repeatedsymbols are placed near each other in the time and/or frequency domain.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an example communications network architecture orsystem 100 in accordance with the present disclosure. The system ornetwork 100 shown in FIG. 1 is for illustration purposes only, andrepresents a cell or sector. Other embodiments of the system 100 may beused without departing from the scope of this disclosure. Reference to“standards” or “specifications” in the text is meant to encompassexisting and future version of the referenced standards orspecifications encompassing the principles of the subject matterdisclosed and claimed herein.

In this example, the system 100 is part of (or communicates with) alarger communication services network 106, and the system 100 includes abase station (BTS) 102 communicating wirelessly with a plurality of userequipment stations (UE) 110, 120 and 130. In one embodiment, the accessservices network (not shown) and system 100 (or portions thereof) is awireless communications network compliant or operating in accordancewith the 3GPP LTE standard or specification, including the UMTS standardwith LTE specification (or later versions). Although only one BTS 102 isshown, the system 100 may, and typically would, include additional BTSsand additional user equipment stations. Each of the BTS 102 and UEs 110,120, 130 generally include one or more antennas and various hardware andsoftware components.

The network 106 may include one or more local area network (“LAN”),metropolitan area networks (“MAN”), wide area network (“WAN”), all orportions of a global network, or any other communication system orsystems at one or more locations, or combination of these, including thepublic switched telephone network (PSTN), Internet, packet networks andthe like. The network typically also includes a BTS backhaul network(not shown) which is a data network utilized for communications betweenthe BTSs and mobile switching centers (MSCs) and/or gateways. Thesenetworks may be configured to include Internet, packet networks and thelike.

Other components, devices or networks may be included in the system 100(and network 106), and FIG. 1 only illustrates but one exemplaryconfiguration to assist in describing the system and operation of thepresent disclosure to those skilled in the art. The system representedin FIG. 1 may be described using different nomenclature or systemterminology, such as use of the term “user equipment” (UE), “accessterminal” (AT) or “mobile subscriber terminals (MS or MT), and “basestation”, “base transceiver station” (BTS), “node B” and “eNode B”, andthe use of any given nomenclature to describe a device within the system100 is not intended to limit the scope of this disclosure.

The BTS 102 has coupled thereto the UEs (several shown). The UEs areoperable for communicating wirelessly with the BTS 102 over an airinterface.

The structure and functionality of a conventional BTS is generallywell-known. A conventional BTS generally includes various componentssuch as processing units, controllers and network interfaces, whichnecessarily include but are not limited to, microprocessors,microcontrollers, memory devices, and/or logic circuitry, and these maybe adapted to implement various algorithms and/or protocols. Noadditional description of the conventional components and softwareprocesses (functionality) of a BTS, other than as notes herein arerelevant for an understanding of the present disclosure, as such arewell known to those of ordinary skill in the art. It will be understoodthat the BTS 102 may be constructed or configured from any suitablehardware, software, firmware, or combination thereof for providing thefunctionality known to those of ordinary skill in the art. The BTS 102will include additional functionality as described below in accordancewith one or more embodiments.

The UEs 110, 120, 130 represent devices utilized by a user or subscriberduring communication sessions over/within the system 100. The UEstypically include a processor, memory, a transceiver and an antenna andmay be constructed or configured from any suitable hardware, software,firmware, or combination thereof for transmitting or receivinginformation over a network. These devices may further include aninput/output device having a microphone and speaker to capture and playaudio information, as well as a camera and/or a display tocapture/display video information. As an example, the UEs may be atelephone, videophone, computer, personal digital assistance, e-maildevice, “smart phone” and the like, or other devices intended toreceiver/transmit wirelessly to the base station. No additionaldescription of the conventional components and software processes(functionality) of the UEs 110, 120, 130, other than as noted herein orrelevant for an understanding of the present disclosure, is provided, asthese are known to those of ordinary skill in the art. It will beunderstood that the UEs 110, 120, 130 may be constructed or configuredfrom any suitable hardware, software, firmware, or combination thereoffor providing the functionality known to those of ordinary skill in theart. The UEs 110, 120, 130 will include additional functionality asdescribed below in accordance with one or more embodiments.

In general terms, the present disclosure describes a method oftransmitting data from a transmitter (e.g., within a base station) toone or more UEs and determining the number of transmit antenna ports inuse by the transmitter.

In operation, to access the network, a UE obtains system and accessconfiguration information from data transmitted within a control channel(e.g., the BCH) broadcast as part of the 10 mSec frames. To properlydecode the data, the UE needs to determine how many transmit antennaports the transmitter is using (i.e., needs to know which transitantenna diversity scheme is used). At the base station, the transmitteris operating in one of a plurality of transmit antenna diversity schemesor modes. Each transmit antenna mode depends on the number of transmitantenna ports in operation.

In one specific embodiment, the transmitter may selectably operate inone of three diversity schemes corresponding to 1, 2 or 4 transmitantenna ports. In other embodiments, the transmitter may operate inaccordance with any one of a number of diversity schemes, with eachscheme utilizing a different number of transmit antenna ports. Though itmay be possible for two or more of the known diversity schemes toutilize the same number transmit antenna ports, it may be more desirablefor each scheme to use a different number of transmit antenna ports.

Depending on the operating mode (scheme), data to be transmitted iscoded according to a predetermined transmit diversity scheme (asdescribed above) that is known by the base stations and the UEs withinthe network. For example, if the transmitter transmits through two (2)transmit antenna ports (in the SFBC mode), the data to be transmitted iscoded into a first format using [S1, S2, S3, S4] and transmitted overtransmit antenna port #1 while the data to be transmitted is also codedinto a different format using [−S2*, S1*, −S4*, S3*] and transmittedover transmit antenna port #2.

Prior to coding and transmitting the BCH transport block data, thetransmitter calculates/computes CRC parity bits (CRC) using the blockdata and appends the computed CRC to the BCH transport block data. Thus,the transmitted BCH data includes two distinct segments or portions: theBCH transport block data and the CRC parity bits. Before transmission, ascrambling sequence (i.e., modulation) is applied to all or a portion ofthe BCH data bits. The applied scrambling sequence depends on the numberof transmit antenna ports in use. In one specific embodiment, thescrambling sequence is applied to all bits of the computed CRC paritybits. In other embodiments, the scrambling sequence may be applied todata bits representing all or a portion of the BCH data, the CRC, orcombination thereof, as desired.

As will be appreciated, the bit scrambling may be accomplished using anyknown scrambling sequence (or otherwise modulated in a known manner).With knowledge of the scrambling sequences that may be applied at thebase station, the original CRC parity bits may be recovered by the UEand this information is thereafter used to determine the number of basestation transmit antenna ports used for transmitting.

It will be understood that a linear scrambling sequence may be utilized.Further, scrambling may be applied those BCH data bits at any point inthe transmit processing party (i.e., prior to coding, after coding, orin between coding processes if more than one coding step is performed),provided the UE de-scrambles at the appropriate point in the receiveprocessing path.

For illustrative purposes, let's assume the BCH carries a total of Xbits of data including Y bits of transport block data and C bits of CRCparity. In this example, a predetermined C-bit mask or scramblingsequence is applied to the original CRC parity bits to generate ascrambled CRC, and the transport block data bits and scrambled CRC bitsare transmitted to the UEs within the BCH. Though any number X, Y and Cbits may be utilized, in one embodiment shown below, C equals 16. Inanother embodiment, X equals 64.

The specific scrambling technique may vary, and in one embodiment, theoriginal CRC bits are modulated, using base 2 arithmetic, with thepredetermined mask (or code). The CRC bits are scrambled according tothe base station transmit antenna port configuration in the table below.

TABLE I CRC mask for BCH Number of transmit antenna ports BCH CRC mask 1<0000000000000000> 2 <1111111111111111> 3 <0101010101010101>According to the embodiment above, when the base station transmits usingonly one transmit antenna port, a logic zero is added to each CRC bitwhich results in a scrambled CRC with data bit values equal to theoriginal CRC bits. When the base station transmits using only twotransmit antenna ports, a logic one is added to each CRC bit whichresults in a scrambled CRC with data bit values inverted (or complement)from the original CRC bits. When the base station transmits using fourtransmit antenna ports, alternating logic zeros and ones are added toeach alternating CRC bit which results in a scrambled CRC with data bitvalues with alternating original and inverted/complement data bitvalues. This is illustrated by the equation c(k)−(p(k)+x(k))mod 2, fork=0, 1, 2, . . . 15, where c equals the resulting scrambled CRC bits, pequals the original CRC parity bits, and x equals the mask bits.

On the receive side, and as noted previously, the UE originally does notknow how many base station transmit antenna ports, and therefore whatdiversity scheme is being used for the downlink transmission. Therefore,the UE decodes the BCH according to the known possible transmit antennadiversity schemes, recovers the BCH data (transport block data andappended CRC), de-scrambles the recovered CRC, computes a CRC on therecovered BCH transport block data, and compares the unscrambled CRC tothe recovered CRC. Based on this process, the UE is able to effectivelyand reliably determine the actual number of transmit antenna portstransmitting from the base station (and thus the actual transmit antennadiversity scheme utilized.

Operation of the system 100 (for an understanding of the presentdisclosure) and general block diagrams of the BTS 102 and the UEs 110,120, 130 will now be described.

Now turning to FIG. 4A, there is shown a block diagram of the BTS 102 inaccordance with the present disclosure. The BTS 102 includes a processor(which may include a digital signal processor) 400, a memory 402, atransceiver 404 having a transmitter 404 a and a receiver (not shown),input/output devices 406, and four antennas 408 a, 408 b, 408 c, 408 d,respectively, representing the transmit antenna ports. Other componentsmay be included, but not shown. Details of the operation and structureof these components, except as necessary to illustrate the operationsand methods described herein, have been omitted. The BTS 102 alsoincludes an interface 410 for communicating with the network 106. Thoughfour transmit antenna ports 408 a-408 d are shown in FIG. 4, the BTS 102may generally include two or more such ports. In addition, thetransceiver 404 may includes multiple transmitters and/or receivers.Typically, the transmitter 404 a includes a digital signal processor,analog transmitter circuitry, logic circuitry and other components(though not shown).

As will be appreciated, the memory 402 stores the predeterminedscrambling sequences, as well as each sequence's association to a giventransmit antenna diversity scheme.

Even though the transmitter 404 a is shown operating as part of awireless base station, the transmitter 404 a and processes performed bythe transmitter 404 a may be utilized and included in other types ofwireless communication devices.

It will be understood that the transmit antenna ports 408 a-408 b may beindividual physical antennas, one or more portions of one or morephysical antenna (e.g., an array of an antenna array), and may belogical in nature. As such, the transmit antenna ports are typicallydifferentiated by utilization of specific reference signals (e.g., R1,R2, R3, R4) at different locations within the data frames transmitted,and could represent different coded orthogonality, polarization or phasedifferences, and the like. Multiple transmit antenna ports work togetherto form antenna diversity, but are not defined by them.

Now turning to FIG. 4B, the transmitter 404 a includes a CRC generator420, a scrambler 430, a channel coder 440 and a transmit antennadiversity coder 450. The transmitter 404 a generates (or receives) BCHtransport block data. Any number of CRC parity bits may be computed anddifferent redundancy schemes may be used. In one specific embodiment,the CRC generator computes a 16-bit CRC.

The scrambler 430 receives and scrambles the computed CRC parity bits(all or a portion thereof) in accordance with a selected one of a numberof predetermined scrambling sequences or masks (hereinafter referred toas a “mask”). Each mask corresponds to a given number of transmitantenna ports (or antenna diversity schemes). One specific embodimentfor a set of antenna configuration masks (see Table I) and a scramblingmethod (modulo 2 addition) has been described above, however, a personof ordinary skill in the art will understand that other embodiments andconfigurations of masks and scrambling methods may be implemented.

It will soon be understood that the scrambler block 430 may optionallyscramble all or a portion of the BCH transport data, all or a portion ofthe CRC parity bits, or a combination thereof, in accordance with theselected mask.

After scrambling, the BCH information bits consisting of the PCHtransport data and scrambled bits (CRC or otherwise) is channel coded,such as by convolution encoding, by the channel coder 440. The encodedbits are provided to the transmit antenna diversity coder 450 whichprocesses and codes the data stream in accordance with the desireddiversity scheme or code (resulting in transmission using 1, 2 or 4transmit antenna ports). The diversity coded signal(s) (e.g., 1, 2 or 4)are then transmitted via the antenna(s) 408 a-408 d. Though not shown,it will be understood that the data symbols are mapped to theappropriate time/frequency locations, along with reference signal anddata from other channels (symbols). These mapped time/frequency symbolsare converted into a time domain symbol (i.e., using an FFT and CPinsertion in standard OFDM methodology.

Other components (not shown) may be provided within the transmit pathfor provide additional functions, such as modulation, rate matching, andRF signal generation. Further, it will be appreciated that the order ofthe components or processes for processing data bits in the transmitpath may be varied, as desired, and other configurations can be used.

Now turning to FIG. 5A, there is shown a block diagram of a UE 110, 120,130 in accordance with the present disclosure. The UE includes aprocessor (which may include a digital signal processor) 500, a memory502, a transceiver 504 having a receiver 504 a and a transmitter (notshown), input/output devices 506, and an antenna 508. Other componentsmay be included, but not shown (such as a network interface). Similarly,details of the operation and structure of these components, except asnecessary to illustrate the operations and methods described herein,have been omitted.

As will be appreciated, the memory 502 has stored the predetermineddescrambling sequences (corresponding to the scrambling sequences usedin the transmitter), as well as each sequence's association to a giventransmit antenna diversity scheme.

Though a single transceiver and antenna are shown, the UE may includemultiple transceivers and/or antennas. Typically, the receiver 504 aincludes a digital signal processor, analog transmitter circuitry, logiccircuitry and other components (though not shown). Even through thereceiver 504 a is shown operating as part of the wireless UEs 110, 120,130, the receiver 504 a and processes performed by the receiver 504 amay be utilized and included in other wireless communication devices.

Now turning to FIG. 5B, the receiver 504 a includes a transmit antennadiversity decoder 520, a channel decoder 530, a de-scrambler 540, andCRC generator/comparator 550. As will be appreciated, the decodeprocessing in the receiver 504 a path is essentially the reverse of thecode processing in the transmitter 404 a.

The UE receives an RF signal (carrying a data frame) transmitted fromthe BTS 102. The received RF signal is composed of one or more RFsignals transmitted from a device, such the base station 102 havingtransmitter 404 a, using one or more transmit antenna ports. Thecomposition of the RF signal depends on the antenna diversity schemeimplemented in the transmitting device.

In one process, the received signal is decoded by the transmit antennadiversity decoder 520 using the known transmit diversity scheme [S1, S2,S3, S4]. The diversity decoded data is delivered to the channel decoder530 for channel decoding and the PCH data (including the transport blockdata and scrambled CRC) is determined (or attempted to be recovered).The de-scrambler 540 applies a descrambling sequence, corresponding tothe scrambling sequence (and mask) used by the transmitter for thetransmit diversity scheme [S1, S2, S3, S4], to the received scrambledCRC to unscramble and recover the original CRC parity bits.

The CRC generator/comparator 550 calculates a CRC based on the decodedBCH transport block data and compares the descrambled CRC to thecalculated CRC. If there is a match, the UE determines that the basestation 102 is transmitting using only one transmit antennaport—identifying the antenna diversity scheme utilized by thetransmitter 404 a. Once the number of transmit antenna ports isdetermined, the UE applies the corresponding antenna diversity scheme tosubsequent transmissions from the base station 102 enabling properdecoding.

As will be appreciated, the mask and descrambling method applied to thescrambled CRC will be chosen to properly recover the original CRC. Inone specific embodiment, the set of antenna configuration masks (seeTable I) and the descrambling method (modulo 2 addition) as used in thetransmitter 404 a is also used in the UE.

In the second process, the received signal is decoded by the transmitantenna diversity decoder 520, but this time using the second knowntransmit diversity scheme which includes both [S1, S2, S3, S4] and[−S2*, S1*, −S4*, S3*]. The two diversity decoded signals are processedby the channel decoder 530, the descrambler 540 and the CRCgenerator/comparator 530 (as described above). Similarly, if matchingoccurs (e.g., the unscrambled CRCs with the calculated CRCs), the UEdetermines that the base station 102 is transmitting using only twotransmit antenna ports.

When using the above process for scrambling CRC bits (e.g., one or morebits) transmitted from a transmitter to a receiver, even if the receivedbits are per perfectly detected when using an incorrect antennadiversity scheme, the likelihood of a correct CRC pass is quite smallthus increasing the reliability of detection.

It will be understood that the received signal may be processedsequentially using each of the known antenna diversity schemes. In thismanner, if the direct diversity scheme processed results in a match ofcomputed CRC and the unscrambled recovered CRC, the diversity schemeused by the transmitter is properly detected. No further detectionprocessing is necessary. In another embodiment, the received signal maybe replicated with each being processed in parallel using all of theknown antenna diversity schemes. Parallel processing may be faster, butmay require more computational resources. Sequential processing may beadvantageous, especially when the first antenna diversity scheme testedas a significantly higher likelihood of being used. As will beappreciated, in the described sequential processing, any one of theknown schemes may be tested first. Further, in one embodiment, thereceiver maintains a log and records the number of times each of thepossible diversity schemes is used in operation. Based on this, thereceiver may dynamically modify its detection process by choosing themost probably diversity scheme based on historical data to be testedfirst, and so on.

In an alternative approach, utilization of resource element (RE) mappingthat is dependent on the number of transmit antenna ports may be used.Though similar to the above described scrambling sequence process, bychanging the RE mapping to be dependent on the number of transmitantenna ports, a correct CRC pass can be made very unlikely. Within thisapproach, there are two strategies. The first strategy is for the changein RE mapping to an ordered cyclic shift, so that the decodingcomplexity can be reduced. The second strategy is to provide for a morerandom rearrangement.

By introducing a scrambling sequence process described above, the waythat different sequences are detected generally requires decoding thefull sequence and checking the CRC. This typically also requires thatchannel estimation, decoding and CRC checking be performed for eachtransmit antenna diversity scheme. To further increase reliability,reduce the likelihood of false positives (detecting a CRC pass for asignal which has been decoded using the wrong diversity scheme) and/ordecrease the computational intensity, utilization or specific scramblingsequences may be used in conjunction with RE mapping. This may helpreduce the number of calculations performed at the UE and improves theeffectiveness of the BCH CRC.

In LTE, low coding rates are achieved by repetition coding of a motherrate ⅓ code. The basic premise is to take advantage of the significantamount of repetition within the BCH coding structure to indicate thenumber of transmit antenna ports. If repeated symbols are placed closeto each other in either the frequency or time domain and scramblingsequences are used which are equivalent to BPSK modulation, then asimpler correlation can detect the number of transmit antenna ports.

For illustration purposes, assume that forty (40) information bits aretransmitted in the BCH. With four (4) OFDM symbols assigned to the BCH,even using RS pattern associated with four transmit antenna ports, 216REs are available. This corresponds to a repetition of 3.6. By assigningthe repeated bits such that, when possible, subcarriers in OFDM symbols0 and 1 (slot 1) and OFDM symbols 2 and 3 (slot 2) of the sub-frameshare the same repeated symbol, a phase rotation between the repeatedsymbols may be detected. The phase rotation in this instance isequivalent to multiplication by +1, or −1, which is in turn equivalentto a specific bit level scrambling sequence. To transmit the threedifferent possibilities for the number of transmit antenna ports, thephase rotations are broken into two elements: one indicating either 1 ormore transmit antenna ports and another indication either 2 or 4transmit antenna ports.

It is believed that reliability of this phase detection is much betterthan the BCH detection (using a scrambling sequence dependent on thenumber of transmit antenna ports) and, further, has no detrimentalaffect on the reliability of the BCH data.

The RE mapping for this approach can be relatively arbitrary, as long aspairs of repeated symbols are placed “near” to each other in either timeor frequency (preferably both) and where the same antenna mapping wouldoccur. “Near” typically means within the coherence bandwidth/coherencetime of the channel and depends on the deployment. Now referred to FIG.6, there is shown an example RE grid illustrating BCH data repeatedwithin the BCH where the repeated symbols are placed near each other.

In yet another approach (not using a scrambling sequence and/or REremapping), a reliability measurement process at the UE may beperformed. In this method, all three antenna diversity schemes aredecoded (as described above) and a measure of how reliable these decodedversions are is taken from the decoder. This reliability measure mayinclude determining a minimum weight at the output of a Viterbi decoder.In this method, the UE would perform full decoding for all antennadiversity schemes. For each scheme that passed the CRC, a measure of therelative accuracy of this decoding would be considered. One option wouldbe the value of the minimum node in the Viterbi decoder of the BCH data.The scheme which had the smallest weight, which corresponds to the mostreliable reception, would be assumed correct. When the multiple transmitantenna diversity schemes (hypotheses) are used to decode the same BCH,the hypotheses with the strong reliability measure is assumed true. Thismay increase the complexity of the receiver because the process cannothave an early stopping criteria and must always decode all hypotheses.

The present disclosure describes a transmitter that transmits a transmitantenna configuration dependent data structure. In other words, a givenset of data that is to be transmitted to a receiver is organized ormodulated in one particular way for a first transmit antennaconfiguration (e.g., when only 1 transmit antenna port is used) and in adifferent way for a second transmit antenna configuration (e.g., whenonly 2 transmit antenna ports are used), and other or additionalconfigurations may be used, if desired. This way, the receiver candistinguish between the two possible transmitter modes (Mode 1: Only 1antenna port; Mode 2: Only 2 antenna ports). Thus, the data structuretransmitted on the antenna port(s) is “dependent” on the transmitantenna configuration. The data structure “dependency” (or the change inthe data structure(s) that can be detected by the receiver) can beaccomplished in different ways, including use of scrambling sequences,RE remapping, repeating certain symbols in a defined pattern or way, orinterleaving (e.g., reordering of channels or groups of bits within thedata frame). These dependent data structure(s) are generated in additionto the coding (reordering of symbols) done by the use of typicaltransmit antenna diversity schemes that are known. Therefore, the datastructure of the transmitted data can be detected at the receiver whichprovides the information that identifies the configuration used by thetransmitter.

In some embodiments, some or all of the functions or processes of theone or more of the devices are implemented or supported by a computerprogram that is formed from computer readable program code and that isembodied in a computer readable medium. The phase “computer readableprogram code” includes any type of computer code, including source code,object code, and executable code. The phase “computer readable medium”includes any type of medium capable of being accessed by a computer,such as read only memory (ROM), random access memory (RAM), a hard diskdrive, a compact disc (CD), a digital video disc (DVD), or any othertype of memory or storage medium.

It may be advantageous to set forth definitions of certain words andphrases used throughout this patent document. The terms “include” and“comprise,” as well as derivatives thereof, mean inclusion withoutlimitation. The term “or” is inclusive, meaning and/or. The phrases“associated with” and “associated therewith,” as well as derivativesthereof, mean to include, be included within, interconnect with,contain, be contained within, connect to or with, couple to or with, becommunicable with, cooperate with, interleave, juxtapose, be proximateto, be bound to or with, have, have a property of, or the like.

While this disclosure has described certain embodiments and generallyassociated methods, alterations and permutations of these embodimentsand methods will be apparent to those skilled in the art. Accordingly,the above description of example embodiments does not define orconstrain this disclosure. Other changes, substitutions, and alterationsare also possible without departing from the spirit and scope of thisdisclosure, as defined by the following claims.

What is claimed is:
 1. A method comprising: receiving from a transmittera plurality of scrambled bits within a data frame; descrambling theplurality of scrambled bits to produce broadcast channel data, whereindescrambling the plurality of scrambled bits uses a selected one of aplurality of unique pre-determined scrambling sequences, each uniquepre-determined scrambling sequence corresponding to a number of transmitantennas used by the transmitter; and determining the number of transmitantennas used by the transmitter according to the selected uniquepre-determined scrambling sequence used to descramble the plurality ofscrambled bits, wherein receiving the plurality of scrambled bitscomprises receiving the plurality of scrambled bits within a primarybroadcast channel in accordance with a Long Term Evolution (LTE)standard.
 2. The method of claim 1, further comprising generating fromthe broadcast channel data transport data and cyclic redundancy check(CRC) data, wherein the CRC data is computed based on the transportdata.
 3. The method of claim 1, wherein the plurality of scrambled bitsare received in a plurality of resource elements.
 4. The method of claim1, wherein the primary broadcast channel uses seventy-two subcarriers.5. The method of claim 4, wherein a period of the primary broadcastchannel is 40 milliseconds.
 6. A communications device for communicatingwith a transmitter in a wireless network, the communications deviceconfigured to: receive from the transmitter a plurality of scrambledbits within a data frame; descramble the plurality of scrambled bits toproduce broadcast channel data, wherein the communications devicedescrambles the plurality of scrambled bits using a selected one of aplurality of unique scrambling sequences, each unique scramblingsequence corresponding to a number of transmit antennas used by thetransmitter; and determine the number of transmit antennas used by thetransmitter according to the selected unique scrambling sequence used todescramble the plurality of scrambled bits, wherein the communicationsdevice receives the plurality of scrambled bits within a primarybroadcast channel in accordance with a Long Term Evolution (LTE)standard.
 7. The communications device of claim 6, wherein thecommunications device is further configured to generate from thebroadcast channel data transport data and cyclic redundancy check (CRC)data, wherein the CRC data is computed based on the transport data. 8.The communications device of claim 6, wherein the plurality of scrambledbits are received in a plurality of resource elements.
 9. Thecommunications device of claim 6, wherein the primary broadcast channeluses seventy-two subcarriers.
 10. The communications device of claim 9,wherein a period of the primary broadcast channel is 40 milliseconds.11. A method for use with Long Term Evolution (LTE) broadcast channeldata, the method comprising: receiving at least a portion of the LTEbroadcast channel data from a transmitter; descrambling the at least aportion of the LTE broadcast channel data using a descrambling sequenceone of a plurality of unique descrambling sequences; and determining thenumber of transmit antennas used by the transmitter based on the uniquedescrambling sequence used to descramble the at least a portion of theLTE broadcast channel data, wherein receiving at least a portion ofbroadcast channel data comprises receiving the at least a portion ofbroadcast channel data within a primary broadcast channel in accordancewith a Long Term Evolution (LTE) standard.
 12. The method of claim 11,wherein determining the number of transmit antennas comprisesdetermining a first scrambling sequence used by the transmitter when thetransmitter uses only one antenna and determining a second scramblingsequence used by the transmitter when the transmitter uses only twoantennas, wherein the first and second scrambling sequences aredifferent.
 13. The method of claim 11, further comprising generatingfrom the broadcast channel data transport data and cyclic redundancycheck (CRC) data, wherein the CRC data is computed based on thetransport data.
 14. The method of claim 11, wherein the at least aportion of broadcast channel data are received in a plurality ofresource elements.
 15. The method of claim 11, wherein the primarybroadcast channel uses seventy-two subcarriers.
 16. A communicationsdevice for receiving Long Term Evolution (LTE) broadcast channel datafrom a transmitter in a wireless network, the communications deviceconfigured to: receive at least a portion of the LTE broadcast channeldata from a transmitter; descramble the at least a portion of LTEbroadcast channel data using one of a plurality of unique descramblingsequences; and determine the number of transmit antennas used by thetransmitter based on the unique descrambling sequence used to descramblethe at least a portion of the LTE broadcast channel data, wherein thecommunications device is further configured to receive the at least aportion of broadcast channel data within a primary broadcast channel inaccordance with a Long Term Evolution (LTE) standard.
 17. Thecommunications device of claim 16, wherein the communications device isconfigured to determine the number of transmit antennas by determining afirst scrambling sequence used by the transmitter when the transmitteruses only one antenna and by determining a second scrambling sequenceused by the transmitter when the transmitter uses only two antennas,wherein the first and second scrambling sequences are different.
 18. Thecommunications device of claim 16, wherein the communications device isfurther configured to generate from the broadcast channel data transportdata and cyclic redundancy check (CRC) data, wherein the CRC data iscomputed based on the transport data.
 19. The communications device ofclaim 16, wherein the at least a portion of broadcast channel data arereceived in a plurality of resource elements.
 20. The communicationsdevice of claim 16, wherein the primary broadcast channel usesseventy-two subcarriers.